1. Field of the Invention
The present invention relates to high purity 1,3-butylene glycol and to production method thereof. More particularly, it relates to high purity 1,3-butylene glycol which a small content of impurities eluted for a specified relative retention time range in HPLC (high performance liquid chromatography) analysis under specified conditions and hence is free of odors and has less change with time and to a method for producing high purity 1,3-butylene glycol by adding a base to crude 1,3-butylene glycol or low quality product, heat treating and distilling.
2. Description of Related Art
1,3-Butylene glycol is a viscous, colorless and transparent, odorless liquid that has a boiling point of 208xc2x0 C. and shows excellent solubility and produces derivatives having excellent chemical stability.
It finds use as a raw material for various synthetic resins, surfactants and also is used as a material for cosmetics, hygroscopic agents, high-boiling solvents, anti-freezes, etc., making the best of its excellent hygroscopicity, low volatility, and low toxicity. In particular, recently, needs for non-toxic, non-irritating 1,3-butylene glycol have been increasing in the field of cosmetics industry since it has excellent properties as a humectant, and odorless butylene glycol is useful as a cosmetic grade.
However, 1,3-butylene glycol obtained by the conventional methods causes changes with time during storage in a tank to generate a slight odor so that it is difficult to store it for a long time.
Therefore, it has been desired to provide 1, 3-butylene glycol free of slight odor after a long-term storage.
JP-A-7-258129 discloses as a method for increasing the yield of odorless product, a method in which at least one compound selected from sodium hydroxide, potassium hydroxide, sodium hydrogen borohydride and potassium borohydride upon distillation for removing high-boiling materials. However, the odorless 1,3-butylene glycol obtained by this method has the problem that it still generates a slight odor due to changes with time after a long-term storage.
Therefore, an object of the present invention is to provide high purity 1,3-butylene glycol having no odor and showing less changes with time and a production method therefor.
The present inventors have made intensive study with view to solving the problem described in JP-A-7-258129 and as a result it has been found that when distillation is performed by adding an alkali metal to a charge stock solution into a de-high-boiling distillation tower, the charge stock solution in the de-high-boiling distillation tower contains a large amount of high-boiling materials and hence the added alkali metal base causes reaction decreasing low-boiling materials and simultaneously generation of low-boiling materials due to decomposition reaction of high-boiling materials. As a result, odor-causing materials can be decreased only to a certain level so that after a long-term storage there occurs a change with time to generate a slight odor.
Accordingly, the present inventors have made further investigation and have found that in a process for distilling and purifying 1,3-butylene glycol, odor-causing materials can be effectively decreased by adding an alkali metal base to crude 1,3-butylene glycol from which high-boiling materials have been removed in advance, heat-treating, distilling off 1,3-butylene glycol to separate the alkali metal base and high-boiling materials as residues, and then distilling off a low-boiling material form the 1,3-butylene glycol fraction. The present invention has been accomplished based on this finding.
Further, the present inventors have found that in HPLC (high performance liquid chromatography) analysis, 1,3-butylene glycol having an absorbance at a specified wavelength of a peak eluted in a specified relative retention time range is odorless and shows less change with time, thus accomplishing the present invention.
That is, the present invention provides the following:
(1) 1,3-Butylene glycol wherein in high performance liquid chromatography analysis under specified conditions, each peak eluted in a relative retention time range of 4.0 to 5.5, taking a relative retention time of 1,3-butylene as 1.0, has an absorbance of 0.02 or less at a measuring wavelength of 210 nm.
(2) 1,3-Butylene glycol as described in (1) above, wherein the 1,3-butylene glycol is produced from acetaldol by a liquid phase hydrogen reduction method.
(3) A method for producing 1,3-butylene glycol, comprising the steps of: adding a base to crude 1,3-butylene glycol free of high-boiling material, heat-treating the mixture and then distilling off 1,3-butylene glycol; and distilling off low-boiling materials from 1,3-butylene glycol.
(4) The method for producing 1,3-butylene glycol as described in (3) above, wherein the 1,3-butylene glycol is produced from acetaldol by a liquid phase hydrogen reduction method.
(5) The method for producing 1,3-butylene glycol as described in (4) above, wherein the crude 1,3-butylene glycol free of high-boiling material is obtained from reaction product obtained from acetaldol by a liquid phase hydrogen reduction method and is distilled from a de-high-boiling material distillation tower after removal of alcohols, of water, and of salts and high-boiling materials.
(6) The method for producing 1,3-butylene glycol as described (3), wherein the base is sodium hydroxide, potassium hydroxide, or a mixture thereof.